1. Field of the Invention
The present invention relates to an optical communication device for performing optical communications based on wavelength multiplexing.
2. Description of the Related Art
An optical communication system using optical fibers has recently been put into practical use in place of the telecommunication system for transmitting electric signals with a view toward achieving prevention of electromagnetic noise, an increase in transfer capacity, a weight reduction in system, simplification of work, etc.
As such an optical communication system, there has conventionally been known a network wherein optical fibers are laid in a house, a vehicle, etc. and light signals having a plurality of different wavelengths are multiplexed and transmitted therethrough. When, for example, an in-house network is used, personal computers and AV devices are connected thereto as terminals.
Meanwhile, when signals are newly added to such an already-existing network and optical communications are made in this state, a method is considered which additionally provides a light source like a white light source, for generating a wide band of wavelengths and filters for passing specific wavelengths or reflecting them. However, when the signals are added to the already-existing network by using the white light source, a problem arises in that they constitute noise for the already-existing wavelengths. It is thus necessary to solve this point of view.
The present invention is constructed such that first and second filters for respectively allowing a first wavelength to pass therethrough and reflecting a second wavelength to be added are placed on an optical transmission line, the first and second wavelengths are multiplexed only on an optical transmission line between the first and second filters, and the second wavelength is set so as not to be transmitted over optical transmission lines other than the optical transmission line referred to above. Since the receiving side for receiving the already-existing first wavelength does not receive the second wavelength if the present invention is constructed in this way, the second wavelength can be prevented from becoming noise.
According to one aspect of this invention, there is provided an optical communication device, comprising: an optical transmission line for transmitting a first wavelength therealong; a light source for emitting light lying within a wide band of wavelengths; a plurality of transmitting means for respectively passing or cutting off a plurality of different second wavelengths other than the first wavelength, lying within the wide band of wavelengths generated from the light source thereby to generate light signals; a first filter for passing the first wavelength and reflecting the second wavelengths thereby to multiplex the first wavelength transmitted through an optical transmission line located on the upstream side and the second wavelengths transmitted through the transmitting means and transmit the resultant band of wavelengths to an optical transmission line located on the downstream side; a second filter for transmitting the first wavelength of the band of wavelengths transmitted from the first filter through the optical transmission line to an optical transmission line located on the downstream side and separating the second wavelengths; and a plurality of receiving means for receiving respective light signals in association with the transmitting means based on the second wavelengths separated by the second filter.
The optical communication device further includes an optical transmission line corresponding to a first branch, for transmitting the band of wavelengths generated from the light source to the first filter through the transmitting means and an optical transmission line corresponding to a second branch, for transmitting the second wavelengths separated by the second filter to the receiving means.
Further, in the optical communication device, a plurality of transmitting means for respectively passing or cutting off a plurality of different second wavelengths thereby to generate light signals are provided on the optical transmission line corresponding to the first branch, and a filter for allowing the plurality of different second wavelengths to branch off and a plurality of receiving means for respectively receiving the respective wavelengths divided by the filter are provided on the optical transmission line corresponding to the second branch.
The optical transmission lines corresponding to the first and second branches are respectively plastic fibers.
Each transmitting means referred to above allows the second wavelength to pass therethrough when turned off and transmits the second wavelength through the optical transmission line. Each receiving means referred to above detects the transmitting means as off upon detection of the second wavelength and detects the transmitting means as on upon non-detection thereof.
The second wavelength referred to above is shorter than the first wavelength.